Package assembly and methods for forming the same

ABSTRACT

A device includes a first package component, and a second package component underlying the first package component. The second package component includes a first electrical connector at a top surface of the second package component, wherein the first electrical connector is bonded to the first package component. The second package component further includes a second electrical connector at the top surface of the second package component, wherein no package component is overlying and bonded to the second electrical connector.

BACKGROUND

In a conventional packaging process, a device die is bonded to a bottompackage component such as a package substrate or a Printed Circuit Board(PCB). The device die includes a plurality of connectors such as bondpads or copper bumps, which are used to bond to the connectors of thebottom package component.

The connectors of the device die are aligned to the connectors of thebottom package component. The electrical interconnection in the bottompackage component is determined by the design of the device die.Accordingly, in the design and the manufacturing of the bottom packagecomponent, the electrical interconnection in the bottom packagecomponent is customized according to the design of the device die. Whenthe design of the device die is changed, the bottom package componentmay also need to be redesigned.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments, and the advantagesthereof, reference is now made to the following descriptions taken inconjunction with the accompanying drawings, in which:

FIGS. 1 through 6 are cross-sectional views of intermediate stages inthe manufacturing of a first-generation package in accordance with someexemplary embodiments;

FIGS. 7 through 9 are cross-sectional views of intermediate stages inthe manufacturing of a second-generation package in accordance with someexemplary embodiments; and

FIG. 10 illustrates a first-generation package comprising a dummy bond.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the embodiments of the disclosure are discussedin detail below. It should be appreciated, however, that the embodimentsprovide many applicable inventive concepts that can be embodied in awide variety of specific contexts. The specific embodiments discussedare illustrative, and do not limit the scope of the disclosure.

A method of designing and packaging package components and the method offorming the same are provided in accordance with various exemplaryembodiments. The intermediate stages of forming the packages areillustrated. The variations of the packaging process are discussed.Throughout the various views and illustrative embodiments, likereference numbers are used to designate like elements.

FIGS. 1 through 6 illustrates the formation of package component 10 andthe packaging using package component 10. The respective packages inFIGS. 3 and 6 are referred to as first-generation packages hereinafter.FIGS. 7 through 9 illustrate the formation of package component 100,which has an identical structure as the package component 10 in FIG. 1,and the packaging using package component 100. The respective package inFIG. 9 is referred to as a second-generation package hereinafter. Thefirst-generation package and the second-generation package may havesimilar functions and similar structures. For example, the packagecomponent 130 in FIG. 9 may be identical to package component 30 inFIGS. 3 and 6. The package component 30 in FIGS. 3 and 6 and the packagecomponent 130 in FIG. 9 may also have most of circuits same as eachother, while a small portion of the circuits, for example, less than 10percent, or less than 5 percent, of the circuits in package components30 and 130 are different from each other. In some embodiments, thepackage in FIG. 9 is an evolved version of the packages in FIGS. 3 and6.

Referring to FIG. 1, package component 10 is formed. In someembodiments, package component 10 is an interposer. In alternativeembodiments, package component 10 is a package substrate such as alaminate substrate or a build-up substrate. In yet other embodiments,package component 10 is a Printed Circuit Board (PCB). Package component10 includes electrical connectors 12 (which further include 12A and 12B)on the top surface 10A, wherein electrical connectors 12 may comprisebond pads, solder bumps, composite electrical connectors including metalpillars covered with solder caps, or the like. Electrical connections 14are built in package component 10, and may interconnect electricalconnectors 12. Electrical connectors 12A and 12B may, or may not, beidentical to each other. In some embodiments wherein package component10 comprises an interposer or a package substrate, electricalconnections 16 are also disposed in package component 10, and used forelectrically coupling electrical connectors 12 to electrical connectors18 at bottom surface 10B of package component 10, wherein surfaces 10Aand 10B are opposite surfaces of package component 10. In alternativeembodiments, for example, when package component 10 is a PCB, noelectrical connection is formed to connect to bottom surface 10B ofpackage component 10.

In some embodiments, dielectric layer 20 is formed to cover electricalconnectors 12 in order to insulate electrical connectors 12 fromexternal detrimental substances such as moisture. Dielectric layer 20may be a top layer of package component 10, or may be an added layer ontop of package component 10. Accordingly, dielectric layer 20 may be, ormay not be, considered as a portion of package component 10. Dielectriclayer 20 may be a solder mask, and hence is referred to as solder mask20 throughout the description, although other dielectric materialshaving adequate insulation ability may also be used.

Referring to FIG. 2, a patterning step is performed to remove someportions of solder mask 20, so that the underlying electrical connectors12A are exposed. Electrical connectors 12B remain covered by solder mask20. The patterning may be performed through an etching step, whereinlithography mask 22 is used for defining the pattern of solder mask 20,for example, through the exposure of a photo resist (not shown) that isused for etching solder mask 20. Lithography mask 22 includes opaquepatterns 24 for blocking light and transparent patterns 26 for allowingthe light to pass through. Although FIG. 2 illustrates that the edges ofsolder mask 20 are spaced apart from electrical connectors 12A, soldermask 20 also covers the edge portions of electrical connectors 12A inalternative embodiments.

Referring to FIG. 3, package component 30 and/or package component 32are bonded to electrical connectors 12A. Each of package components 30and 32 may be a device die including active devices such as transistorstherein, or may be a package. Each of package components 30 and 32 mayalso be a stand-alone passive device such as an inductor, a transformer,a balun, or the like. Electrical connectors 12B are not bonded to anyoverlying package components. Electrical connectors 12B may includeelectrical connectors 12B1, which is overlapped by package component 30.Electrical connectors 12B further include electrical connectors 12B2,which are not overlapped by any package components. Electricalconnectors 12B2 are also misaligned with package components 30 and 32.The bonding of package components 30 and 32 may be performed throughsolder bonding, direct metal-to-metal bonding, or the like.

As shown in FIG. 3, electrical connectors 12B, although not bonded, maystill be electrically coupled to electrical connectors 12A, which arebonded to overlying package components 30 and/or 32, and/or electricallycoupled to electrical connectors 18B, which is on the bottom side ofpackage component 10. Accordingly, although electrical connectors 12Bare not bonded, electrical connectors 12B may, or may not, beelectrically floating. Throughout the description, in the packages,electrical connectors 12B that is not bonded to other package componentsare referred to as dummy connectors.

FIGS. 4 through 6 illustrate cross-sectional views of intermediatestages in the formation of a package in accordance with alternativeembodiments. Unless specified otherwise, the materials and formationmethods of the components in these embodiments are essentially the sameas the like components, which are denoted by like reference numerals inthe embodiments shown in FIGS. 1 through 3. The details of the likecomponents shown in FIGS. 4 through 6 may thus be found in thediscussion of the embodiment shown in FIGS. 1 through 3. Referring toFIG. 4, package component 10 is formed. Package component 10 isessentially the same as the package component 10 shown in FIG. 1, exceptthat pre-solder layers 23 are formed as a top portion of each ofelectrical connectors 12. Next, as shown in FIG. 5, solder mask 20 ispatterned, and electrical connectors 12A and 12B are exposed.Lithography mask 122 that is used for the patterning step is thusdifferent from the lithography mask 22 in FIG. 2.

In the following steps, as shown in FIG. 6, package components 30 and/or32 are bonded to electrical connectors 12A, while electrical connectors12B are not bonded to any overlying package components. Solder layers 23may be exposed after the bonding process, and act as the protection ofthe underlying metal features. In alternative embodiments, whenpre-solder layers 23 are formed, solder mask 20 may be omitted. Theresulting structure is essentially the same as shown in FIG. 6, exceptthat there is no solder mask 20.

FIGS. 7 through 9 illustrate the formation of the second-generationpackage, wherein the design of package component 10 is reused. Referringto FIG. 7, package component 100 is formed. Package component 100 may beidentical to the package component 10 in FIG. 1. Particularly, theportions of package component 10 not including solder mask 20 areidentical to the portions of package component 100 not including soldermask 20. Solder mask 20 in FIG. 1 may be identical to, or may bedifferent from solder mask 20 in FIG. 7.

Next, as shown in FIG. 8, a patterning step is performed to remove someportions of solder mask 20, so that the underlying electrical connectors12A are exposed. The patterning may be performed through an etchingstep, wherein lithography mask 122 is used for defining the pattern ofsolder mask 20, for example, through the exposure of a photo resist (notshown), with the photo resist used as the etch mask for etching soldermask 20. Lithography mask 122 is different from lithography mask 22 inFIG. 2. Accordingly, in addition to the electrical connectors 12A, atleast one of electrical connectors 12B is exposed. In some embodiments,one or more of electrical connectors 12B are exposed, and one or more ofelectrical connectors 12B remain covered by solder mask 20. Inalternative embodiments, all of electrical connectors 12A and 12B areexposed.

FIG. 9 illustrates the bonding of package components 130, 132 and/or 134to package component 100. Each of package components 130, 132, and 134may be a device die including active devices such as transistorstherein, a package, a stand-alone passive device, or the like. In someexemplary embodiments, package component 130 in FIG. 9 and packagecomponent 30 in FIG. 3 or FIG. 6 are identical to each other. Inalternative embodiments, package components 130 and package component 30in FIG. 3 or FIG. 6 are similar to, and not identical to, each other.For example, package components 130 and package component 30 may haveover 90 percent circuit identical to each other, while the remainingcircuits are different from each other. At least one electricalconnector 12B is bonded with an overlying package component (such as 130and 134, as illustrated). In some embodiments, all of electricalconnectors 12B are bonded with overlying package components. Inalternative embodiments (not shown), some of electrical connectors 12Bremain not bonded, and may be bonded in a third-generation package (notshown). The un-bonded electrical connectors 12B may be exposed, or maybe covered by solder mask 20.

FIG. 10 illustrates a package formed in accordance with alternativeembodiments. In these embodiments, electrical connectors 12A are bondedto the overlying package components 30 and 32 through active bonds 41,which may be solder bonds, for example. Active bonds 41 are configuredto pass voltages and/or currents between the bonded package components.Dummy bond 40 is also made, for example, through dummy solder bump 40.The respective underlying electrical connector 12B is thus also referredto as a dummy connector. The dummy bond 40 bonds electrical connector12B to overlying package component 30. Dummy bond 40 may be electricallycoupled to other portions of the resulting package through theelectrical connections 14/16 in package component 10. Accordingly,during the operation of the resulting package, dummy bond 40 may beapplied with voltages/signals. Dummy bond 40, however, as indicated bythe “x” signs, is not electrically coupled to functional circuit 42,which may include transistors, for example, and other active bond pads31A of package component 30 that are bonded to electrical connectors12A. Accordingly, no current flows through dummy bond 40. Furthermore,package component 30 includes electrical connector 31B, which is a dummyelectrical connector that is electrically floating when packagecomponent 30 is not bonded to package component 10. In theseembodiments, dummy electrical connector(s) may provide mechanicalsupport, and share the stress in the package, although they do not haveelectrical functions.

In the embodiments, by adopting the identical design for packagecomponents 10 (FIGS. 1 and 4) and 100 (FIG. 7), the cost for designingand manufacturing package component 100 is reduced. Since the packagesin FIG. 9 may be the later generation of the packages in FIGS. 3 and 6,at the time the first-generation package is designed, additionalelectrical connectors 12B and the respective electrical connections maybe reserved for the second-generation packages. At the time thesecond-generation packages are formed, a simple modification may be madeto modify the lithography mask 122 in FIG. 8, and the cost related tothe design of package component 100 (FIG. 9), the design and themanufacturing of the lithography masks that are used for manufacturingpackage component 100, and the like, is saved.

In accordance with embodiments, a device includes a first packagecomponent, and a second package component underlying the first packagecomponent. The second package component includes a first electricalconnector at a top surface of the second package component, wherein thefirst electrical connector is bonded to the first package component. Thesecond package component further includes a second electrical connectorat the top surface of the second package component, wherein no packagecomponent is overlying and bonded to the second electrical connector.

In accordance with other embodiments, a device includes a first packagecomponent and a second package component. The second package componentincludes a first electrical connector at a top surface of the secondpackage component, wherein the first electrical connector is bonded tothe first package component through an active bond. The second packagecomponent further includes a second electrical connector at the topsurface of the second package component. The second electrical connectoris bonded to the first package component through a dummy bond. A thirdelectrical connector is at the top surface or a bottom surface of thesecond package component, wherein the second electrical connector iselectrically coupled to the third electrical connector.

In accordance with yet other embodiments, a method includes bonding afirst package component with a second package component, and bonding athird package component with a fourth package component. The second andthe fourth package components are substantially identical to each other.Each of the second and the fourth package components includes a firstelectrical connector at a top surface of a respective one of the secondand the fourth package components, wherein the first electricalconnector of the second package component is bonded to the first packagecomponent, and the first electrical connector of the fourth packagecomponent is bonded to the third package component. Each of the secondand the fourth package components further includes a second electricalconnector at the top surface of the respective one of the second and thefourth package components, wherein no package component is overlying andbonded to the second electrical connector of the second packagecomponent, and wherein the second electrical connector of the fourthpackage component is bonded to an overlying package component.

Although the embodiments and their advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the embodiments as defined by the appended claims. Moreover,the scope of the present application is not intended to be limited tothe particular embodiments of the process, machine, manufacture, andcomposition of matter, means, methods and steps described in thespecification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the disclosure.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps. In addition, each claim constitutes a separateembodiment, and the combination of various claims and embodiments arewithin the scope of the disclosure.

What is claimed is:
 1. A device comprising: a first package component;and a second package component comprising: a first electrical connectorat a top surface of the second package component, wherein the firstelectrical connector is bonded to the first package component through anactive bond; a second electrical connector at the top surface of thesecond package component, wherein the second electrical connector isbonded to the first package component through a dummy bond; and a thirdelectrical connector at the top surface or a bottom surface of thesecond package component, wherein the second electrical connector iselectrically coupled to the third electrical connector, and wherein thefirst package component comprises a fourth electrical connector bondedto the second electrical connector, and wherein the fourth electricalconnector is a dummy connector.
 2. The device of claim 1, wherein thefourth electrical connector is not electrically coupled to any otherbond pads of the first package component.
 3. The device of claim 1,wherein the fourth electrical connector is not electrically coupled toany functional circuit in the first package component.
 4. The device ofclaim 1 further comprising a third package component bonded to the thirdelectrical connector, wherein the third electrical connector is at thetop surface of the second package component.
 5. The device of claim 1,wherein the third electrical connector is at the bottom surface of thesecond package component.
 6. The device of claim 1, wherein the first,the second, and the third electrical connectors have an identicalstructure, and are formed of same materials.
 7. A method comprising:bonding a first package component with a second package component; andbonding a third package component with a fourth package component,wherein the second and the fourth package components are substantiallyidentical to each other, and wherein each of the second and the fourthpackage components comprises: a first electrical connector at a topsurface of a respective one of the second and the fourth packagecomponents, wherein the first electrical connector of the second packagecomponent is bonded to the first package component, and the firstelectrical connector of the fourth package component is bonded to thethird package component; and a second electrical connector at the topsurface of the respective one of the second and the fourth packagecomponents, wherein no package component is overlying and bonded to thesecond electrical connector of the second package component, and whereinthe second electrical connector of the fourth package component isbonded to an overlying package component.
 8. The method of claim 7further comprising: before the step of bonding the first packagecomponent, performing a first patterning step to pattern a topdielectric layer of the second package component and to expose the firstelectrical connector of the second package component, wherein the secondelectrical connector of the second package component remains covered bythe top dielectric layer of the second package component; and before thestep of bonding the third package component, performing a secondpatterning step to pattern a top dielectric layer of the fourth packagecomponent and to expose the first and the second electrical connectorsof the fourth package components.
 9. The method of claim 7, wherein thefirst and the third package components are identical to each other. 10.The method of claim 7, wherein the first and the third packagecomponents are similar and not identical to each other.
 11. The methodof claim 7, wherein the second electrical connector of the secondpackage component is overlapped by the first package component.
 12. Themethod of claim 7, wherein the second electrical connector of the secondpackage component is misaligned with the first package component, and iscovered by a solder mask, and wherein the method further comprisesbonding a fifth package component to the second electrical connector ofthe fourth package component.